Corals Produce Molecules To Attract Microbes That Keep Them Healthy

Science
I write about the ocean, climate change, and the future of our planet.

School of fish on corals in Suizokukan, Nagoya-shi, JapanSagar | UnSplash

Coral reefs are charismatic ocean habitats known for the immensity of life that inhabits them. The corals themselves are also incredibly diverse - despite their sedentary lifestyles, they possess many characteristics that allow them to take advantage of the surrounding environment. For example, in shallower parts of the ocean where sunlight penetrates the water, corals harbor microscopic algae (called “zooxanthellae”) that photosynthesize*. In exchange for this safe habitat, the algae convert light into sugars and other molecules that help the corals grow and survive.

Corals also have a tight relationship with the unique microbes that exist on their surfaces, which oftentimes help them respond to environmental change (an organism and the microbes associated with them are collectively known as a “holobiont”). And, a new study by Michael A. Ochsenkühn and colleagues shows that corals are able to regulate their microbial communities using molecules they produce themselves.

The researchers examined 18 separate coral aggregations consisting of Acropora and Platgygyra corals along the Abu Dhabi coast. They collected multiple seawater samples, starting with water closest to the corals’ surface and then progressively sampling water at greater and greater distances from the corals. The water samples revealed that the corals were surrounded by several molecules that became less common further away from the corals. These molecules – signalers, anti-bacterials, and chemical attractors – are likely being used to draw in microbes that will maintain the coral’s health, while deterring disease-causing microbes.

The researchers were also able to classify how microbial communities differ between healthy corals and those infected with “white syndrome”. Identifying microbial communities affiliated with unhealthy corals can help predict disease outbreaks, as these microbes may reside on the corals or in nearby seawater prior to the onset of an infection.

"This is the first glimpse we have of what corals do in their immediate surroundings to adapt to their environment,” says Dr. Amin, co-author of the study. “If we understand the types of molecules corals need to maintain a healthy surface microbiome, we may be able to predict when diseases and bleaching occur and perhaps even prevent them.”

-

* In the deep ocean where no sunlight is available, many organisms partner with microscopic life forms that are “chemosynthetic” and convert hydrogen sulfide and methane into a nutritious product that their hosts can use.

I am an ocean and climate scientist interested in how human activity is altering our coastal oceans. I am currently a PhD student at the University of California, Davis studying the influence of climate change on the food we grow along the California coast (mussels, oysters,...